Facebook clearly know that they are suffering in terms of driving people to purchase as a result of seeing a link/post on the site. They are looking at every angle which turns out to include using the button “want”.
“I want that” will replace “I like that”. Sounds like petulance will replace affection. Do we really want people to go around “wanting” rather than “liking” ? It’s a tactic employed by rival Pinterest and is a way to encourage shared “wanted” items to be bought for/by friends.